Working with Stainless Steel - How would you build this? - Building a teak helm pod for a whaler

So I'm in the final stages of building a teak helm pod for my Boston Whaler and I need some sort of plate to keep water from getting into the steering shaft hole, spread the load from the bolts holding the steering to it and something decorative. Normally the hydraulic steering assemblies come with this but I'm still using a teleflex cable so my cover is going to be a little larger than usual.

I need approximately a 6" OD washer. If I bought a piece of 316 Stainless flat stock (~$23 at McMaster),  what are the chances I could make this myself and have it look good? I'm not much of a metal worker so I don't know how feasible this is. Could I get a good enough circle with an angle grinder?  Any ideas?

The piece I'm talking about is the large washer under the steering wheel:

[img]https://www.thehulltruth.com/attachment.php?attachmentid=892490&d=1504631729[/img]

[img]https://www.marlinmag.com/sites/marlinmag.com/files/styles/medium_1x_/public/images/2016/02/27_0.jpg?itok=SI2swLW5[/img]

Side question - what am I doing wrong with these image tags?

You can use a grinder to get it to shape, but stainless has a nasty habit of warping if you get it hot (worse for flat sheet/plate).

If the material is thin enough, you can use basic tools like snips/shears to get the shape taking small cuts to make it easier.

Drilling holes is doable without warping, but you will want to make sure you have good bits.

All I've got is for the side question; In the old forumware, you'd just wrap things in HTML img tags (<img src="your link here" />); on the new one, I've just been hitting the Image button in the comment panel and pasting the link into the URL field. Seems to work for your link (I don't know whether you can put HTML directly into the new comment panel EDIT: no, if you could put HTML tags in here, I'd have a broken link instead of the example tag in the first sentence):

Ideally it would be pretty thick, somewhere between 1/8" and 1/4".

Were I asked to make that I would start with a sheet of SS and use a 6" hole saw on it.  Then I would clamp it down and using the same arbor and pilot bit I would mount a hole saw with the proper ID of the hole. Then I would true it up on the lathe.

The problem here is that a 6" diameter hole saw would need to turn ~45 RPM on 308SS and I can't think of a single drill press or hand drill that will go that slow with any torque. I would end up putting my mill in back gear and use lots of coolant at 80RPM.

Is 0.250" too thick? McMaster has 303 discs in 1/4" That is the bulk of the work done for you.

In reply to Jumper K. Balls :

I didn't realize that was an option. 1/4" would work but I just checked and 316 stainless is $58! I'll have to think about that.

What would happen if it turned faster? I have access to a drill press. Would I need to buy a metal bit or could I sacrifice a wood bit?

In reply to Enyar :

It would cut about 1/16" of an inch and burn the teeth off the blade. That heat that is created will then harden the berkeley out of the stainless leaving it uncuttable.. It will chatter like crazy making the hole the wrong size and your neighbors would come from blocks away to ask you to stop making that terrible noise.  Kidding but not kidding. If you could get a drill press into the ~100 RPM range and flooded it with cutting oil you might be able to keep it cool enough.

And a Bi-Metal 6" hole saw is about $45 so all of the sudden buying a $60 disc doesn't seem so expensive.

My local steel yard would probably cut a 1/4" slab of 6" 316 at price per pound plus $15 for the cut. Probably around $35. You can check your local yard. 

Also are you set on 316? That is one of the harder to work with alloys. Also 1/4" seems really thick to me.

If 304 is acceptable try this or this

In reply to Jumper K. Balls :

I'm not, but it's going to be used in a saltwater environment so I was thinking 316 was best. I'm going to head to the local yard this weekend and see what they can do for me.

Ransom said:

All I've got is for the side question; In the old forumware, you'd just wrap things in HTML img tags (<img src="your link here" />); on the new one, I've just been hitting the Image button in the comment panel and pasting the link into the URL field. Seems to work for your link (I don't know whether you can put HTML directly into the new comment panel EDIT: no, if you could put HTML tags in here, I'd have a broken link instead of the example tag in the first sentence):

Thanks!

In reply to Jumper K. Balls :

Nice! I should be able to polish that to a mirror finish correct? In reference to your ebay finds.

Oh yes. Those CNC Plasma cut discs would probably be much easier to polish than a band saw cut disc from the steel yard.

You could get that cut out at a plasma cutter shop for not much.  Probably cut perfect to your specs for fifty  bucks.  Then just polish it with whatever you want from elbow grease to a buffer. 

Or you could cut it out yourself with a hacksaw, grinder, and time, then do the polishing thing.

Plasma cutter with a guide is the quickest and easiest way that I know of. If you can get it to Flint I will be happy to help